1. Field of the Invention
This invention generally relates to weaving of preforms and particularly relates to weaving of preforms used in bonding of components at structural joints.
2. Description of the Prior Art
When joining components in a structural joint, layers of fabric infused with a polymer resin can be used to join the components. For example, two components are brought to the desired positions and orientation, and layers of composites are adhered to the outer surfaces of the components: one portion of the fabric adhering to one component, another portion adhering to the other component. Multiple layers of fabric are stacked to increase the strength of the joint and to form a radiussed intersection. While this method works well, the joint can be improved by having fibers that extend through the intersection of the components, connecting the composite layers on both sides of the joint. A 3-D, woven, textile preform provides for fibers that extend through the intersection of a joint. The preform is infused with a resin that is cured to form a rigid polymer matrix surrounding the fibers of the preform.
Weave patterns for woven composite textiles have been used in the past which can provide for various shapes of three-dimensional preforms. However, these weave patterns were typically single-layer connectors, for example, U.S. Pat. No. 4,671,470 to Jonas, in which is disclosed an H-shaped connector for connecting a wing spar to a sandwich skin structure. Also, three-dimensional preforms have been woven to fill gaps formed during layup of composite layers into tight radius intersections. A gap-filling preform is disclosed in U.S. Pat. No. 5,026,595 to Crawford, Jr., et al.
However, these prior-art preforms have been limited in their ability to withstand high out-of-plane loads, to be woven in an automated loom proces, and to provide for varying thickness of portions of the preform. Weave construction and automation of preform weaving was in its infancy and provided only a small advantage over conventional laminated, fiber-wound, or braided composites, limiting the versatility of the preforms.
A three-dimensional weave architecture for weaving preforms has fill fibers woven to provide layer-to-layer interlocking of layers of warp fiber as well as interlocking of fibers within each layer. The woven preform transfers out-of-plane loading through directed fibers to minimize inter-laminar tension. The preform has a base and at least one leg extending from the base, the base and leg each having at least two layers of warp fibers. The fill fibers follow a weave sequence which carries them through part of the base, then into the legs, then through the other portion of the base, and back through the base to return to the starting point of the fill tow. The leg may be connected at a single- or distributed-column intersection, and the intersection may be radiussed. The outer ends of the base and legs may have tapers formed from terminating layers of warp fibers in a stepped pattern.